Diadenosine polyphosphates and the control of cyclic AMP concentrations inisolated rat liver cells

Extracellular diadenosine polyphosphates (Ap,,A), through their interaction s with appropriate P-2 receptors, influence a diverse range of intracellula r activities. In particular, Ap(4)A stimulates alterations in intracellular calcium homeostasis and subsequent activation of glycogen breakdown in iso lated liver cells. Here we show that, like ATP, Ap4A and other naturally oc curring diadenosine polyphosphates attenuate glucagon-stimulated accumulati on of cyclic AMP in isolated rat liver cells. The characteristics of Ap(4)A - and ATP-dependent modulation of glucagon-stimulated cyclic AMP accumulati on are similar. These results are discussed in the context of the repertoir e of intracellular signalling processes modulated by extracellular nucleoti des, (C) 1999 Federation of European Biochemical Societies.